A new photonic approach of microwave waveform generator based on time-domain synthesis is proposed and experimentally demonstrated, in which two single-drive Mach-Zehnder modulators biased at quadrature point are severed as optical pulse carvers and various microwave waveforms can be generated by carving and overlapping optical field envelopes. The theoretical analysis and simulation are developed. In experiment, a square waveform with 50% duty cycle, triangular waveform with full duty cycle, and sawtooth (or reversed-sawtooth) waveform with 50% duty cycle are generated. Furthermore, a frequency doubling sawtooth (or reversed-sawtooth) waveform with full duty cycle is also obtained.

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A new photonic scheme for various waveforms generation has been proposed and demonstrated. In the scheme, two cascaded single-drive LiNbO Mach-Zehnder modulators serve as pulse shaper and the polarization-dependent character of the modulators is fully exploited and utilized. By arranging the polarization states of the incident light, two different spectra are achieved on two orthogonal polarization components respectively. Finally, the desired waveforms can be obtained by superimposing the photocurrents of the two orthogonal signals on a photodetector. The detailed theoretical analyses and simulations are given. In the experiment, square-shaped waveform, triangular waveform and sawtooth (or reversed-sawtooth) waveform are obtained successfully. Furthermore, an approach to smoothing the sawtooth waveform with fewer harmonics is suggested and verified.

We propose and demonstrate a new photonic approach for triangular waveform generation. Based on an optical signal with sinusoidal envelope, an injection-locking process in a distributed-feedback semiconductor laser diode is employed to carry out the desired harmonic signal generation, and then the tailored signal is synthesized by the superimposition of these signals with proper power ratio and time delay. In this method, the conventional spectral line manipulating is transferred to individual signal envelope control, which reduces the technical requirement while the flexibility and accuracy is improved. In the experiment demonstration, triangular waveforms with the repetition frequencies of 9, 10, and 12 GHz are successfully generated. The results well agree with the theoretical predication and show great potential to realize arbitrary waveform generation.

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